|M.Sc Student||Zimmerman Fernando|
|Subject||Pulsed Plasma Thruster-Assisted Formation Keeping of|
Nano-Satellites under J2 and Drag
|Department||Department of Aerospace Engineering||Supervisor||Professor Pinchas Gurfil|
|Full Thesis text|
Multiple satellites flying in formation or performing cluster flight can potentially accomplish the goals of larger and more expensive platforms, benefiting from faster and cheaper construction, which facilitates redundancy and increases the mission return.
Usually used for attitude control, de-orbiting and drag compensation, the use of micro pulsed plasma thrusters (µPPTs) as a primary propulsion system for cluster keeping has not been thoroughly examined. In addition, no work has been reported comparing the performance of µPPTs and the more commonly used cold gas thrusters in maintaining a cluster for long periods of time.
In this thesis we develop algorithms for long-term cluster flight of nanosatellites flying on near-circular low Earth orbits (LEOs). The development of these algorithms is performed by taking into account that either a µPPT or a cold gas thruster is the primary propulsion system of each of the satellites in the cluster. In addition, we systematically compare the performance of these two propulsion systems by evaluating them at each stage of the algorithms development, with the main goal being understanding the advantages and disadvantages of each one of the propulsion systems in maintaining bounded cluster flight for long periods of time.
The main results are the accomplishment of one year cluster flight for maximum inter-satellite distance bounds ranging from 100 km to 250 km, using either cold gas thrusters or micro pulse plasma thrusters. Simulations performed to evaluate the presented algorithms show a tenfold decrease in the satellites fuel consumption when using micro pulse plasma thrusters compared to using cold gas thrusters.
The main contribution of this thesis, in addition to the feasibility demonstration of long-term cluster flight using µPPTs, is the systematic comparison between both propulsion systems, which highlights their advantages and disadvantages. The conclusion is that µPPTs are a feasible option for nanosatellites cluster keeping at near circular LEOs, in particular if some sacrifice can be done in terms of the time needed for cluster initialization. Then, the mission can be enhanced by utilizing the PPT's smaller dimensions and weight, which might enable redundancy (and thus increasing reliability), increase the payload's weight and dimensions or decrease the entire satellite's weight and dimensions.